Allow installd to stat asec files and /data/media files.

Addresses denials such as:
avc: denied { getattr } for comm="installd" path="/data/app-asec/com.vectorunit.red-1.asec" dev="dm-0" ino=578229 scontext=u:r:installd:s0 tcontext=u:object_r:asec_image_file:s0 tclass=file

avc:  denied  { getattr } for  pid=262 comm="installd" path="/data/media/0/Android/data/com.google.android.apps.maps/cache/cache_vts_tran_base_GMM.m" dev="dm-0" ino=124930 scontext=u:r:installd:s0 tcontext=u:object_r:media_rw_data_file:s0 tclass=file

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

(cherry picked from commit d2622fda)

Change-Id: Iac46236ee583dee11a7e6518a9e8eca25c59e9ba